Esters of 3,5,6-trichlorosalicylic acid are quite useful as components of formulations which produce light by a chemiluminescent reaction. Various prior art processes exist for preparing such esters such as are described in U.S. Pat. No. 5,194,666. These prior art processes utilize acid esterification catalysts such as sulfuric acid and p-toluenesulfonic acid to bring about the esterification of the 3,5,6-trichlorosalicylic acid with a C.sub.3 -C.sub.20 alcohol such as n-pentanol in the presence of an aromatic solvent such as xylene. The principal disadvantage of such prior art processes is that a significant amount of the alcohol is converted to by-product ether due to a competing etherification reaction.
The '666 patent is directed towards an improvement in the prior art esterification processes in that it virtually excludes the competing etherification reaction by substituting a titanium ester or titanium chelate or mixtures thereof for the acid catalysts. The titanium esters disclosed in the '666 patent are tetralkyl titanates, preferably those embraced by the general formula (R'O).sub.4 Ti, wherein the R' groups are independently C.sub.2 -C.sub.10 alkyl groups such as tetraisopropyl titanate or tetra-n-butyl titanate. The titanium chelates disclosed in the '666 patent include titanium acetonyl acetonate chelate and titanium ethyl acetoacetate chelate.
Although the titanium esters and titanium chelates employed as esterification catalysts in the '666 patent appear to be effective in esterifying 3,5,6-trichlorosalicylic acid without a significant production of by-product ether, they are nevertheless disadvantageous in comparison to the materials employed in the present invention. The glycol titanates and stannates employed as catalysts herein for the esterification of 3,5,6-trichlorosalicylic acid may be utilized in significantly lower quantities than the esterification catalysts employed in the '666 patent. Moreover, the esterification process of the present invention entails a reaction time which is radically shorter than that of the '666 patent. The smaller quantity of catalyst and shorter reaction time with virtually no ether by-product formation results in considerable savings in manufacturing costs for the instant process as compared to that of the '666 patent.